Increased levels of antibiotic resistant bacteria as a result of antibiotic use, either clinical or agricultural, is well documented. Further information is needed about environmental factors, other than antibiotic use, which can contribute to increased levels of bacteria with genes for antibiotic resistance. Two such environmental factors are ultraviolet radiation (UV) and the presence of heavy metals. Genes for UV and heavy metal resistances, like those for antibiotic resistance, are frequently plasmid-borne. Thus the presence of UV, heavy metals, or both in the environmental could also the incidence of resistance to antibiotics. The specific aims of this project are to determine incidence of antibiotic resistance in aquatic ecosystems influenced by UV and heavy metals, to determine patterns of multiple resistance and whether these multiple resistance can be transferred by conjugation, to determine levels of UV and heavy metal resistances in these ecosystems, and to determine what correlations may be present between resistances and the environmental factors. The streams to be utilized in this study lie in the Colorado mineral belt at elevations from 8000 to 12,000 feet and receive intense natural radiation. Sites will be located in various geological areas to determine the influence of a variety of heavy metals. ICP analyses of samples will permit an accurate evaluation of the kinds and amounts of metals present. This research will provide ecological data relevant to the understanding of antibiotic resistance, especially as it relates to aquatic sources. It would be particulary useful with regard to drinking water and recreational waters as potential sources of resistant bacteria.